<template>
  <div class="back-to-top" @click="backToTop"
       v-show="showReturnToTop" @mouseenter="show"
       @mouseleave="hide">
    <i :class="[bttOption.iClass]"></i>
  </div>
</template>

<script>
import {scrollIt} from '@/plugs/scrollIt' // 引入动画过渡的实现
export default {
  name: 'sys-top',
  props: {
    text: { // 文本提示
      type: String,
      default: '返回顶部'
    },
    textColor: { // 文本颜色
      type: String,
      default: '#f00'
    },
    iPos: { // 文本位置
      type: String,
      default: 'right'
    },
    iClass: { // 图标形状
      type: String,
      default: 'iconfont icon-huidaodingbu'
    },
    iColor: { // 图标颜色
      type: String,
      default: '#f00'
    },
    iFontsize: { // 图标大小
      type: String,
      default: '32px'
    },
    pageY: { // 默认在哪个视图显示返回按钮
      type: Number,
      default: 200
    },
    transitionName: { // 过渡动画名称
      type: String,
      default: 'easeOutQuad'
    }
  },
  data: function () {
    return {
      showTooltips: false,
      showReturnToTop: false
    }
  },
  computed: {
    bttOption () {
      return {
        text: this.text,
        textColor: this.textColor,
        iPos: this.iPos,
        iClass: this.iClass,
        iColor: this.iColor,
        iFontsize: this.iFontsize
      }
    }
  },
  methods: {
    show () { // 显示隐藏提示文字
      this.showTooltips = true
    },
    hide () {
      this.showTooltips = false
    },
    currentPageYOffset () {
      console.log(this.pageY)
      // 判断滚动区域大于多少的时候显示返回顶部的按钮
      window.pageYOffset > this.pageY ? this.showReturnToTop = true : this.showReturnToTop = false
    },
    backToTop () {
      scrollIt(0, 200, this.transitionName, this.currentPageYOffset)
    }
  },
  created () {
    window.addEventListener('scroll', this.currentPageYOffset)
  },
  beforeDestroy () {
    window.removeEventListener('scroll', this.currentPageYOffset)
  }
}
</script>

<style scoped lang="scss">
  .back-to-top {
    position: fixed;
    bottom: 5%;
    right: 5%;
    z-index: 9998;
    cursor: pointer;
    width: 50px;
    height: 50px;
    background-color: rgba(0, 0, 0, 0.52);
    border-radius: 5px;
    i {
      font-size: 32px;
      line-height: 32px;
      display: inline-block;
      position: relative;
      text-align: center;
      margin-top: 7px;
      width: 100%;
      height: 100%;
      border-radius: 5px;
      cursor: pointer;
      transition: all 0.3s linear;

    }
    &:hover {
      background-color: rgba(0, 0, 0, 1);
      color: #fff;
    }

  }
</style>
